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First study links specific types of air pollution to autism

Kathleen Blanchard's picture
Air pollution during pregnancy now linked to autism risk

Exposure to high levels of pollution during pregnancy is now linked to double the risk of having a child with autism, according to Harvard School of Public Health (HSPH) researchers.

The new study is the first large investigation to look at autism rates across the U.S. relative to inhaling certain air pollutants.

Autism pollution link raises concerns

Andrea Roberts, research associate in the HSPH Department of Social and Behavioral Sciences says the study is concerning. The finding showed 20 to 60 percent of women studied lived in areas of high pollution where autism risk was also found to be higher.

For the study that started in 1989 the Harvard researchers extracted data from the Nurses' Health Study II that involved 116,430 nurses.

The investigation looked at 325 women who had a child with autism and 22,000 who did not. The researchers matched levels of pollution at the time of birth with the disorder; also taking into account other factors such as home environment, smoking during pregnancy, income and education.

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Estimates of the amount of air pollution exposure at the time women gave birth was extracted from and Environmental Protection Agency (EPA) database.

Diesel and mercury in the air linked to double the risk for autism

Particulate matter containing diesel or with mercury in the air was found to double the chance that a woman would have a child with autism in 20 percent of areas with the highest amount of the airborne pollutants; compared to 20 percent in areas with the lowest levels.

Other types of air pollutant linked to autism included lead, manganese, methylene chloride, and combined metal exposure.

Interestingly, the disorder has been linked to toxins in the past. The most recent debate has been whether mercury exposure in vaccines contributes to autism. Last year, a study published in the New England Journal of Medicine again found no link between the brain disorder and mercury in vaccines. One of the reasons is because mercury does not cross the blood-brain barrier, according to the researchers. The study, however, was small.

The organization Autism Speaks has been advocating for more studies to help understand how environmental exposure to toxins, genes and timing of exposure might be contributors to the disorder that affects more males than females.

The new study is the first to explore specific types of toxins in the air and autism risk.

Senior author Marc Weisskopf, associate professor of environmental and occupational epidemiology at HSPH, said in a press release, the study suggests measuring metals and other pollutants in the bloodstream during pregnancy or in newborns could help provide evidence that specific air pollutants increase the chances of autism. The hope from the researchers is to develop interventions to protect pregnant women from exposure to the airborne toxins.